Connective tissue provides a framework in which the cells and organs of the body reside. A primary component of connective tissue in vertebrates is the extracellular matrix. The two main structural constituents of the extracellular matrix are polysaccharides, which form a gel-like ground substance, and fibrous proteins embedded in the ground substance. Two of the most common of these fibrous proteins are collagen and elastin. Collagen fibers are formed by self-association of collagen fibrils, which are themselves assembled by the cross-linking of triple-helical collagen molecules. This cross-linking is catalyzed by lysyl oxidase (LOX) and related enzymes (“lysyl oxidase-like” or “LOXL”), all of which contain a catalytic domain capable of deaminating the ε-amino groups of lysine and hydroxylysine residues, resulting in conversion of peptidyl lysine to peptidyl-α-aminoadipic-δ-semialdehyde (allysine). Allysine residues are able to condense spontaneously with each other, resulting in crosslinking of collagen molecules.
The involvement of the extracellular matrix in various pathologies (including, for example, fibrosis and metastasis) has become increasingly apparent. See, for example, WO 01/83702 (Nov. 8, 2001); WO 2004/047720 (Jun. 10, 2004); WO 2007/126457 (Aug. 11, 2007); US 2006/0127402 (Jun. 15, 2006); US2007/0225242 (Sep. 27, 2007); US 2009/0053224 (Feb. 26, 2009); US 2009/0104201 (Apr. 23, 2009); Csiszar (2001) Prog. Nucleic Acid Res. and Molec. Biol. 70:1-32; Kirschmann et al. (2002) Cancer Research 62:4478-4483. Since lysyl oxidase and lysyl oxidase-like enzymes play a key role in the formation of the extracellular matrix, by crosslinking collagen, they represent important therapeutic targets. Hence, methods to screen for inhibitors of these collagen-crosslinking enzymes, methods for identifying molecules that bind to these enzymes, and sources of collagen-crosslinking activity for various therapeutic uses (e.g., wound healing) would all be desirable.